Hitherto, reactors employing catalysts have been used in various fields and optimally designed depending on the purpose.
On the other hand, in recent years, attention has been paid to using hydrogen as fuel because of no generation of global warming gas such as carbon dioxide in terms of the global environmental protection, and of the high energy efficiency. Particularly, attention has been paid to fuel cells because they can directly convert hydrogen to electric power and enable the high energy conversion efficiency in the cogeneration system utilizing generated heat. The fuel cells have been hitherto employed under the particular conditions such as in the space development and the ocean development. Recently, however, the development has advanced toward using them for automobile and household distributed power supplies, and fuel cells for portable devices have also been developed.
With respect to the fuel cells for portable devices, reduction in size is essential so that reduction in size of reformers that produce hydrogen gas by steam reforming hydrocarbon-based fuel has been studied variously. For example, there has been developed a microreactor having a silicon substrate or a ceramic substrate formed with a microchannel and carrying a catalyst in this microchannel (Laid-open Unexamined Patent Publication No. 2002-252014).
However, since the conventional microreactor, including the microreactor for hydrogen production, carries the catalyst in the microchannel, it is necessary to select a material of the microreactor taking into account catalyst supportability thereof and therefore there have been those instances where there is no alternative but to use a material that is poor in heat utilization efficiency. Further, there has been a problem that, in the process of applying a catalyst into a microchannel, cleanness of a substrate surface where the microchannel is formed is lost to thereby impede the microreactor production which is implemented by joining substrates together. Further, there have been those instances where a catalyst supported in a microchannel is extremely contaminated or deactivated in a later process and therefore there has also been a problem that usable catalysts are limited and the production process management is difficult. Moreover, the conventional microreactor has a low reaction efficiency and therefore a microreactor with a higher reaction efficiency has been demanded.